1. Field of the Invention
The present invention relates to an ophthalmologic photographing apparatus capable of switching between an infrared light observation and a visible light observation, and a photographing method therefor.
2. Description of the Related Art
Known methods of fundus photography include non-mydriatic photography of photographing a fundus without a mydriatic instilled into a subject's eye, and mydriatic photography of photographing a fundus with a mydriatic instilled into a subject's eye. In the non-mydriatic photography, a fundus is photographed while a subject's eye is in a state of natural mydriasis in a dark place, and generally, an observation is made with use of infrared light to prevent miosis of a subject's eye from occurring during an observation.
On the other hand, in the mydriatic photography, a fundus is photographed while a subject's eye is forced into a mydriasis state by a mydriatic. Therefore, miosis does not occur even if visible light is projected on a subject's eye, and generally, an observation is made with use of visible light. However, in some cases, an observation may be made with use of infrared light to reduce a burden on a subject's eye.
Japanese Patent Application Laid-Open No. 9-66030 discusses an ophthalmologic photographing apparatus that can be used for both the non-mydriatic photography and the mydriatic photography. In this apparatus, an operator can switch between the non-mydriatic photography function and the mydriatic photography function, and an infrared light observation is performed during the non-mydriatic photography and a visible light observation is performed during the mydriatic photography.
Fluorescence photography, in which a subject's eye is photographed with a fluorescent agent intravenously injected into the body of the subject, requires an examination time of normally 10 to 30 minutes or longer. During an early stage of fluorescence, since the amount of a change in an observed image due to an inflow of the fluorescent agent is large, a number of photographs are taken in a short time. However, during a later stage of fluorescence, since the fluorescent agent has been circulated throughout the eye fundus and, therefore, the amount of a change in an observed image is small, a photographing interval is increased. When there are many subjects to be photographed, another subject may be photographed by utilizing an idle time during the first subject's photographing interval in the later stage of fluorescence, in order to improve the overall photographing efficiency.
As an apparatus that can be used in such a case, Japanese Patent Application Laid-Open No. 2004-180705 discusses an apparatus that can simultaneously implement a plurality of examinations.
However, an operator may forget to switch from the visible light observation to the infrared light observation, when a subject to be now examined is changed from a person who has undergone a visible light observation with a mydriatic instilled into his/her eye, to a person who is about to undergo an infrared light observation without a mydriatic instilled into his/her eye. Further, when a subject's eye without a mydriatic instilled therein is observed with use of infrared light, an operator may switch from the infrared light observation to the visible light observation by an operational mistake.
In such a case, when visible light is projected to a subject's eye without a mydriatic instilled therein, the subject' eye becomes miotic. Once the subject's eye becomes miotic, a waiting time may be required until the subject's eye naturally becomes mydriatic, and, therefore, the photographing efficiency is impaired.
On the other hand, since daily operations habituate an operator to a certain extent, if an apparatus requires a special operation to an operator only for a part of functions thereof, the operator may have an uncomfortable feeling to the operation of the apparatus, which may result in an induction of an operational mistake.